Research Summary

Our research involves the development and applications of conventional and innovative analytical techniques to study the environmental fate and transport of emerging contaminants. Some of the questions we intend to answer are: (1) how fast and by what means do these chemicals degrade?, (2) what are the major breakdown products of these compounds in the environment?, (3) how do environmental conditions affect the persistence and mobility of these contaminants? and (4) are these compounds of significant ecotoxicological concern?

Analytical Chemistry plays a key role in our investigations to answer several fundamental questions in environmental chemistry. We use modern instruments such as LC/MS/MS, CZE, ICP/MS and GC/MS/MS, in combination with bioassays as tools to study many important environmental processes. Development of effective sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), and solid-phase microextraction (SPME) are critical in obtaining reliable and accurate results.

Environmental Fate and Biodegradation of Veterinary Antibiotics and Estrogens

Residues of antibiotics and natural estrogens excreted by animals enter the environment via cropland application of manure that is used as fertilizer. Constant exposure to low levels of antibiotics can lead to the emergence of antibiotic-resistant microorganisms in the environment, while presence of estrogens in surface runoff can cause endocrine disruption in fish in the receiving streams. Due to the potential ecological and human health risks associated with these manure-borne chemicals we are investigating the factors affecting their mobility and persistence in soil. Our research also aims to determine the impact of advanced anaerobic digestion systems in reducing antibiotics, antibiotic resistance genes, and endocrine disrupting chemicals found in animal manure.

Fate and Plant Uptake of Pharmaceuticals from Urine-Based Fertilizers Used in Agriculture

Source separated urine has the potential to become a sustainable nutrient source for agricultural applications. At the same time, removing urine at the source results in lower energy requirements at wastewater treatment plants, a reduction in fresh water consumption from toilets, improvements in wastewater composition that favors biological N removal, and an opportunity to remove contaminants that are concentrated in urine from less complex and reduced volume waste streams. This research will evaluate the feasibility of urine separation technology at the source, and will determine the safety of using precipitated urine as fertilizer for agricultural crops. This approach offers a sustainable and cost-effective step to reducing the amount of pharmaceuticals that reach the aquatic systems, as well as provides a low-cost source of essential nutrients (nitrogen and phosphorous) for crop production. The goals of this research are: [1] to evaluate the removal efficiency of pharmaceuticals in urine and determine how pretreatments (storage, precipitation) impact degradation of pharmaceutical and biological contaminants; [2] compare the efficacy of using natural urine and urine derived products (e.g. struvite) as agricultural fertilizers; and [3] evaluate the potential of agricultural crops to take-up pharmaceuticals.

Treatment of Pharmaceutical Contaminants in Wastewater

Residues of human pharmaceuticals enter the environment from discharges of wastewater treatment plants (WWTP). Our studies focus on the identification of pharmaceutical metabolites resulting from their biodegradation in activated sludge systems. In many cases, we find that the absence of the parent pharmaceutical from the WWTP effluents does not necessarily mean that the compound has been completely eliminated, but instead has only been partially transformed. We are also investigating the efficiency of pharmaceutical removal by advanced oxidation process using UV/H2O2 followed by biofiltration. We have observed that recalcitrant pharmaceuticals can be converted into more biodegradable transformation products by UV/H2O2 treatment. Our study shows that it is important to identify transformation products that are persistent because long-term exposure to some of them may potentially lead to detrimental ecological effects.

Metabolism of PBDEs by Human Cytochrome P-450s

In this study, we are characterizing the enzyme- and congener-specific metabolism of polybrominated diphenylethers (PBDEs) in humans. We are also investigating qualitative and quantitative differences in PBDE metabolism that are related to genetic variability in key biotransforming enzymes. This research will ultimately better inform future mechanistic and epidemiological studies investigating the potential of PBDEs and their metabolites to produce neurobehavioral / neuro developmental disorders. In addition, these studies will lead to the identification of potential genetic biomarkers that contribute to inter-individual variability in the bioactivation of PBDEs, and ultimately the relative susceptibility of individuals to potential adverse effects of these agents. In addition, we are developing a sensitive analytical method using GC/MS/MS for the trace analysis of hydroxylated PBDE metabolites in human serum and milk. The method can be used for large-scale epidemiological studies that can provide insights on the role of hydroxylated PBDE metabolites in the development of neurobehavioral disorders in children.